PHP正则表达式将纯文本URL转换为链接，除非它已经存在

Question

I have a php string $tweet that looks like this...

This is a sample tweet https://tr.co/sdfhnjn3

But sometimes it can look like this...

This is a sample tweet <a href="https://tr.co/sdfhnjn3">https://tr.co/sdfhnjn3</a>

I am wanting to convert all https://tr.co links to actual a href links unless they are already in that format.

I know I can convert the links with Regex but can I also check if they are already a link using it as well?

Answer 1

Without going into incredibly sophisticated syntax trying to match bits and pieces of a url, you can disqualify already-tagged urls using (*SKIP)(*FAIL) and then only match the urls from your domain.

Code: (Demo) (Regex101)

$tweets = [
    'This is a sample tweet https://tr.co/sdfhnjn3',
    'This is a sample tweet <a href="https://tr.co/sdfhnjn3">https://tr.co/sdfhnjn3</a>',
    'This is a sample tweet https://example.com/sdfhnjn3',
    'This is a sample tweet <a href="https://example.com/sdfhnjn3">https://example.com/sdfhnjn3</a>'
];

var_export(preg_replace('~<a [^>]+>.*?</a>(*SKIP)(*FAIL)|https?://(?:www)?tr.co/\S*~', '<a href="$0">$0</a>', $tweets));

Output:

array (
  0 => 'This is a sample tweet <a href="https://tr.co/sdfhnjn3">https://tr.co/sdfhnjn3</a>',
  1 => 'This is a sample tweet <a href="https://tr.co/sdfhnjn3">https://tr.co/sdfhnjn3</a>',
  2 => 'This is a sample tweet https://example.com/sdfhnjn3',
  3 => 'This is a sample tweet <a href="https://example.com/sdfhnjn3">https://example.com/sdfhnjn3</a>',
)

*only the first element was actually updated, the others did not qualify.